Suction valve for piston-type compressors



Aug. 26, 1969 R. F. KHLER ET AL 3,463,184

sUCTIoN VALVE FOR PIsToN-TYPE CQMPREssoRs 'Filed Jan'. l0, 1968,

Otto F/-oml oZcZ United States Patent O U.S. Cl. 137-512.15 5 Claims ABSTRACT OF THE DISCLOSURE A suction valve for piston-type compressors, comprising a lifting device for the valve plate for the infinitely variable delivery control. The valve plate is subdivided into an outer plate area and an inner plate area, only the inner plate area being impinged upon by the lifting device.

Background of the invention The delivery of piston-type compressors may be subject to infinitely variable regulation by keeping the valve plate of the suction valve open beyond the stroke reversal stage by means of a lifting device acting upon it through the valve seat, so that part of the medium drawn in by the compressor is again forced to ilow back into the suction pipe. This so-called back-flow or impact pressure control is frequently applied to advantage and distinguishes itself above all by its largely loss-free operation. However, the usefulness of this control system is restricted to small and medium-size valves up to a valve plate diameter of approximately 200 or 250 millimeters, because experience goes to show that when applied to the control of larger valve plates, this method is liable to subject the valve plate to premature wear. In order to remedy this situation, a plurality of small valves have been substituted for the large suction valve since the for-mer have been found to be more suitable for infinitely variable back-flow regulation. However, a drawback of this system resides in the fact that the splitting up of the cross-sectional area available for the installation of the valves considerably impairs the free passage of the medium flowing therethrough.

It is, however, not always necessary for infinitely variable regulation by the back-flow system to keep the entire cross-section of the suction valve open, but in many instances an aperture covering only about percent of the valve cross-section is known to suffice. IIn such cases therefore, the continuous single slotted plate of largesized plate valves has been replaced by two or more annular or plate-shaped closing elements arranged in concentrical relation to, and independently from, each other, only the closing element located in the central area of the valve being impinged upon by the lifting device, the peripheral area of the valve cross-section being controlled by slidingly guided individual rings which are not subject to regulation. The main drawback of this system is due to the fact that slidingly guided valve-closing elements are not universally applicable, such as for example, in conjunction with unlubricated compressor units for infiammable or explosive gases and that sliding guidance calls for the provision of special guide surfaces in the Valve involving additional expense.

Summary of the invention It is the object of the invention to eliminate the shortcomings of the known devices and to provide for smooth and innitely delivery control also with large-sized suction valves without the need for more than one closing Patented Aug. 26, 1969 element and for seat and valve guard elements of special design.

The invention provides for a suction valve comprising a valve seat and a valve guard in spaced relation to the valve seat, ports in the valve seat and in the valve guard, a valve plate between the valve seat and the valve guard, the said valve plate consisting of a plurality of concentrical n'ngs interconnected by means of radial Webs, and means for lifting the valve plate olf the valve seat for the purpose of regulating the delivery of the piston-type compressor by keeping the suction valve open, the valve plate being subdivided into an outer plate area comprising at least the outermost plate ring, and an inner plate area, flexible guide means being arranged between the two plate areas, the said guide means interconnecting the two plate areas comprising at least one plate ring and permitting a relative motion of the two plate areas in the direction of the valve axis, the inner plate area of the valve plate alone being impinged upon by the means for lifting the valve plate.

The two plate areas as well as the interconnecting ilexible guide means of the suction valve according to the invention are cast integral, the outer plate area being connected with the inner plate area by means of the said guide means and guided thereby in a manner avoiding friction. Consequently, it is not necessary to make special provision for the guiding of the uncontrolled outer plate area, so that the conventional seat and guard members of uncontrolled valves may be used to advantage. Furthermore, the design according to the invention tends to improve the plate movements, since the inner regulated plate area is guided by the guide means leading to the unregulated outer plate area functioning like an ordinary suction valve in a plane-parallel relation to the valve seat in a better manner than is the case with an ordinary valve plate of the same size without the provision of guide means acting upon its outer periphery. Since safety against fracture of valve plates is generally greater where the plates move in a plane-parallel relation to the valve seat, the design according to the invention also ensures a longer life of the valve plate.

Flexible guide arms for ring-plate valves are known to be responsible for slight contortions of the valve plate during the stroke movement due to the fact that they are shortened when bending out of the plane of the plate. In the suction valve according to the invention this tendency towards distortion is liable to produce additional stresses in the guide means because when the inner plate area is kept open by the lifting device, the uncontrolled outer plate area comes to rest upon the valve seat at an earlier stage, so that during the subsequent closing the inner plate area a torsional tendency is exerted upon the said inner plate area both by the guide arms located in the plate center and by the intermediate guide means arranged between the two plate areas. In order to avoid objectionable stresses when using a valve plate comprising a hub which is clamped in the valve axis and from which flexible guide arms extend ina circumferential direction to the inner plate area, the guide means provided between the two plate areas emerge from the inner plate area and extend to the outer area in a circumferential direction which is contrary to the circumferential direction in which the guide arms emerging from the hub and adjoining the inner plate area extend, the hub of the valve plate being preferably clamped in the plane of the valve seat. As a result of this simple arrangement, the torsional tendency exerted by the two sets of guide means upon the inner plate area acts in the same direction so that the valve plate is allowed to rotate -freely and additional stresses in the guide means are avoided.

Preferably the guide means arranged between the two plate areas cover ports provided in the valve seat in the same manner as the other rings of the valve plate, so that no aperture cross-section of the valve is lost by this arrangement of the guide means. In order to avoid overloading of the flexible guide means, particularly in the case of major strokes of the valve plate, the said guide means preferably extend over at least one quarter of the circumference of the valve plate, so as to present an adequate length and suflicient flexibility. Instead of liexible guide-means comprising a single ring of the plate only, it is also possible to use so-called chain-type guides consisting of two or more plate rings linked together chainfashion in a peripheral direction.

Brief description of the drawing Further optional details of the invention will appear from the following description of an embodiment of the invention with reference to the accompanying drawing in which:

FIG. l is an axial cross-sectional view of a suction valve with a lifting device according to the invention taken on line I-I of FIG. 2, and

FIG. 2 is a plan view of the valve plate.

Description of a preferred embodiment According to the embodiment of the invention shown in the drawing the valve comprises a valve seat 1 and a valve guard 2 connected with the valve seat 1 by means of a central bolt 3 and a nut 4 screwed thereon. Between the valve seat 1 and the valve guard 2 a valve plate 5 and a spring plate 6 are located. However, the spring means might also be constituted =by helical springs arranged in the valve guard 2. The damping plate preferably also used in this conjunction has been omitted from the drawing to ensure greater clarity. Flexible guide arms serve for the frictionless guidance of the valve plate clamped together with its hub by means of a washer 7 between the valve seat 1 and the valve guard 2, the hub of the valve plate S directly resting on the valve seat. The spring plate 6 comprising flared spring arms 8 is clamped to the valve guard 2 by means of the washer 7.

The lifting device comprises lifting pins 9 guided in the valve seat 1, for example in bores of the radial connecting webs extending between the ports, and serving to transmit the regulating forces to the valve plate 5. At their extremities facing away from the valve plate 5 the lifting pins 9 have collars 10 for the lifting springs 11 supported by a pressure plate 12. The pressure plate 12 is secured to a bushing 13 which is slidable in the direction of the valve axis on a cylindrical guide means 14 defined by an extension of the bolt 4. The bushing 13 is subject to the action of a control gear indicated by a plunger 15 in the embodiment shown. The restoring spring for the pressure plate 12 is designated by reference number 16.

As appears from FIG. 2, the valve plate 5 is designed as a slotted plate comprising a number of concentrical rings 17 interconnected by means of radial webs 18. In the middle of the valve plate a hub 19 is provided from which two flexible guide arms 20 extend for the frictionless guidance of the valve plate 5. The valve plate 5 is subdivided into an outer plate area A delined by the two outermost rings 17, and into an inner plate area B composed of the four inner rings adjoining the guide arms 20. The rings 17 of each of the plate areas A and B are essentially rigidly interconnected by means of a plurality of webs 18. On the other hand, flexible guide means 21 are provided between the two plate areas A and B, the said guide means Ibeing produced from a plate ring 17 -by obliquely ripping up connecting webs 18, and extending over one fourth of the periphery of the plate. The flexible guide means 21 thus permit a relative movement of the two plate areas A and B in the direction of the valve axis.

In the valve comprising a built-in valve plate 5 as illustrated in FIG. l, the inner plate area B is guided without friction by means of the guide arms 20, while the outer plate area A -is also guided without friction by 4 means of the flexible guide means 21 adjoining the outer periphery of the inner plate area B. For the infinitely variable regulation of the delivery of a piston-type cornpressor equipped with the suction valve shown in the drawing, only the inner plate area B is lifted olf the valve seat 1 by means of the lifting device shown in FIG. 1 using lifting pins 9 acting upon the valve plate 5 in the places designated by reference number 9 in FIG. 2. No lifting pins are, however, provided above the outer plate area A, so that this plate area functions as an ordinary suction valve, the comparatively long flexible guide means 21 allowing the outer plate area A to positively rest on the valve seat 1 even with the inner plate area B lifted and consequently adjoining the valve guard 2. In addition, the guide means 21 improve the parallel guidance of the inner plate area B during its stroke motion.

The guide arms 20 of the valve plate 5 shown in FIG. 2 provided in the middle of the plate extend from the hub 19 clockwise in a circumferential to the inner plate area B, whereas the guide means 21 lead counterclockwise from the inner plate area B to the outer plate area A. During the stroke motion of the valve plate 5 incorporated in the valve illustrated in FIG. 1, the inner plate area B is thereby rotated by means of the two sets of guide means 20, 21 in the same direction, so that objectionable stresses in the guide means 20, 21 due to opposing trends of rotation are avoided. For the same purpose, the valve plate S is clamped directly on to the valve seat 1 instead of the conventional clamping approximately in the middle between the valve seat 1 and the valve guard 2, so that the .guide arms 20 are bent out of the plane of the plate in one direction only and rotate the inner plate area B only in one direction. Fixing the valve plate in this manner offers the further advantage of preventing the guide arms 2t) in view of their inertia from continuing to vibrate when the valve plate impinges upon the valve seat, since they come to rest upon the valve seat 1. Experience goes to show that particularly in the case of regulated suction valves wherein the closing impact is rather hard, these continued vibrations of the guide means are liable to cause premature breakage of the Aguide means.

As appears linally from FIG. l, the plate ring forming the guide means 21 also covered ports of the valve seat 1, so that in spite of the flexible guide means 21 the available cross-sectional area of the valve seat 1 is fully used for the passage of the pressure medium.

The design of the lifting device is immaterial for the purposes of the present invention. The same effect can be obtained if the lifting device comprising lifting pins kept mobile by means of springs as provided in the embodiment hereabove described are replaced by a rigid lifting grip of conventional design, such as for example, a welded sheet metal grip having lifting fingers extending through the ports of the valve seat.

We claim:

1. Suction valve for piston-type compressors, comprising a valve seat and a valve lguard in spaced relation to the valve seat, ports in the valve seat and in the valve guard, a valve plate between the valve seat and the valve guard, the said valve plate consisting of a plurality of concentrical rings interconnected by means of radial webs, and means for lifting the valve plate off the valve seat for the purpose of regulating the delivery of the piston-type compressor by keeping the suction valve open, the valve plate being subdivided into an outer plate area comprising at least the outermost plate rin-g, and an inner plate area, flexible guide means being arranged between the two plate areas, the said guide means interconnecting the two plate areas comprising at least one plate ring and permitting a relative motion of the two plate areas in the direction of the valve axis, the inner plate area of the valve plate alone being impinged upon by the means for lifting the valve plate.

2. A suction valve according to claim l, in which the valve plate is provided with a hub clamped in the axis of the valve and from which lexible guide arms extend in a circumferential direction to the inner plate area, the said guide arms ensuring frictionless guidance of the valve plate during its movements irl the valve, wherein the guide means formed by at least one plate ring and provided between the two plate areas extend from the inner plate area to the outer plate area in a circumferential direction which is contrary to the direction of the guide arms extending from the hub and adjoining the inner plate area.

3. A suction valve according to claim 2, wherein the hub of the Valve plate is clamped flush with the upper surface of the valve seat.

4. A suction valve according to claim 1, wherein the guide means defined by at least one plate ring cover ports provided in the valve seat.

5. A suction valve according to claim 1, wherein the guide means dened by at least one plate ring extend at least over a quarter of the circumference of the valve plate.

References Cited UNITED STATES PATENTS WILLIAM F. ODEA, Primary Examiner W. H. WRIGHT, Assistant Examiner U.S.C1. XR. 

